This invention relates to a gas blast circuit breaker and more particularly, to a gas blast circuit breaker which is suitable for comprising an odd number of circuit breaking units within an enclosed container.
A puffer type gas blast circuit breaker has been known as a high-voltage, large-capacity circuit breaker. The puffer type gas blast circuit breaker generally comprises a breaking unit within an enclosed container filled with an arc extinguishing gas, for example, SF.sub.6 gas of a single pressure. The breaking unit has a pair of contacts which are separable relative to each other and a compressing device which compresses the arc extinguishing gas in corelation to the separating action between the paired contacts. The gas thus highly pressurized by the compressing device is blasted at the arc occurring between the contacts to extinguish it.
It is generally required for the high-voltage, large-capacity gas blast circuit breaker to use at least two breaking units constituting one breaking assembly. More particularly, movable contacts of the two breaking units are connected to a common insulator operating rod, and the insulator operating rod is driven by an actuator provided separately so that the two movable contacts are actuated simultaneously.
Accordingly, this type of circuit breaker usually has an even number of breaking units with a few exceptions where a single breaking unit is utilized. For example, a circuit breaker which is of a larger capacity next to a circuit breaker with two breaking units has four breaking units or two breaking assemblies. Such a construction system is advantageous for facilitating the increase or decrease of the capacity of the circuit breaker merely by increasing or decreasing the number of the breaking assemblies.
However, the recent improvements in gas blast circuit breakers and advances in current breaking technology have been very large and this trend has contributed to a rapid improvement in the current breaking capacity of a single breaking unit.
From this background, it may be disadvantageous to construct the circuit breaker of a larger capacity next to the circuit breaker of two breaking units by always assembling such four breaking units. Apart from this reason, there is also a demand for circuit breakers of an intermediate capacity.
Briefly, in the conventional gas blast circuit breaker, two breaking units constitute one breaking assembly. Typically, the assembly is arranged such that a supporter called a bracket is secured to an insulator supporting cylinder which is held stationary with its axis aligned with the radius of a tank or enclosed container, and the movable contacts are supported on opposited ends of the supporter. A single insulator operating rod inserted in the insulator supporting cyclinder is adapted to transmit a switching operation force simultaneously to the movable contacts of the respective two breaking units.
In the case of four breaking units connected in series, for example, two sets of the breaking assemblies are arranged. Each breaking assembly is provided with one insulator operating rod and all of the rods are simultaneously operated by a single actuator. The actuator is connected to the movable contacts through respective operation force transmission mechanisms having substantially the same structure in order to avoid mismatching in switching operation of the breaking units. The operation force transmission mechanism includes the insulator operating rod and a link mechanism which are adapted to mechanically connect the actuator to the movable contacts. More particularly, the link mechanism is disposed between the insulator operating rod belonging to each breaking assembly and the actuator and enclosed in a casing. Accordingly, for the purpose of avoiding mismatching in switching operation of the breaking units, it is desirable to arrange the casings as close as possible to each other.